I made a video showing real-time reflections that I have added to my path tracer:
This uses the same room (based on a real one in my house) that the previous video did but with reflections added. I also thought that spheres would be a better way for a viewer to understand reflections than rectangular blocks and so I implemented the ability to have interpolated shading normals.
One thing that I always like in papers is when there is a row of spheres with some progressively-varying difference in a material property. I only had room for three spheres in a row for the size of spheres I wanted and the narrow room in my house, but it was fun to at least create a miniature version of the kind of diagram that I always enjoy seeing.